In HA "auto" and "heat_cool" are two different modes and one did not replaced the other. Both are still in use and are not interchangeable.
Originally HADB was trying to translate HE modes to compatible HA modes but this cause numerous incompatibilities. Since last year this behavior was change to match whatever the HA thermostat was advertising regardless of HE build-in modes. Hence the HE auto mode is no longer translated to heat_cool. This allow for all available mode on a HA thermostat to be usable which was not the case before.
Unfortunately the choices for mode selection are fix. A possible workaround would be to overload the thermostat mode command with all the possible HA modes.